Sintered refractory material



June 18, 1963 -r. w. RATCLIFFE SINTERED REFRACTORY MATERIAL 2 Sheets-Sheet 1 Filed Aug. 2, 1960 INVENTOR 72-MP4E 14 P? TCL IFFE ATTO R N EY 2 Sheets-Sheet 2 INVENTOR T. W. RATCLIFFE SINTERED REFRACTORY MATERIAL Tex/p4: M 7? CLIFFE June 18, 1963 Filed Aug. 2, 1960 United States Patent 3,094,424 STNTEREB REFRACTGRY MATERHAL Temple W. Ratciii'fe, Bearer, Pa, assignor to The Babcock & Wilcox Qompany, New York, N.Y., a corporation of New Jersey Filed Aug 2, 1960, Ser. No. 46,919 Claims. (Cl. lite-59) This invention relates to a sintered ceramic refractory material, and more particularly to a sintered ma-gnesitechrome pouring nozzle for use in the casting of metals.

In casting metals, it is customary to pass molten metal from a melting furnace through confined channels such as ladles and the like to ingot molds where the metal is solidified. During passage of the molten metal to the mold, impurities may be entrained with the metal stream with adverse effects in the solidified casting. Such impurities may be in the form of metal oxides or may originate by erosion from or reaction with the materials defining the molten metal flow path. The problem of impurity entrainment in molten ferrous metals and alloys, such as steel, is particularly serious since ferrous alloys are easily oxidized and in either their pure or oxidized state react with known refractory materials. Various procedures for handling molten steel have heretofore been de-.

veloped to minimize the formation of impurities and to reduce or eliminate the inclusion of slag and/or oxides in the cast ingot. Such procedures usually involve the teeming of the molten steel from a furnace into a transfer ladle and bottom pouring of the steel from the ladle either directly or through an intermediate vessel to the casting mold. Bottom pouring from a ladle or other vessel is usually favored, since a major portion of the impurities will float on the surface of the molten metal and the discharge of such impurities with the molten metal can be avoided. With the molten metal being discharged through a nozzle in the bottom of a ladle or other vessel, means must be provided for controlling the flow of metal through the nozzle. This usually necessitates the use of a stopper rod for shut-off purposes, and sometimes the stopper is used as a valve in conjunction with a selected cross-sectional flow area of the nozzle. Under such conditions, the materials constituting the nozzle must be sufficiently soft to provide a seat for the stopper rod so as to seal the nozzle when the stopper is in its closed position. In addition, the nozzle must be able to withstand the erosive elfect of the metal passing therethrough and to withstand the variations in temperatures to which it is subjected.

The properties of the materials constituting a pouring nozzle become particularly critical when the nozzle is used in any metal pouring process where a uniform delivery rate and a smooth surfaced consolidated stream is required such as in the multiple nozzle pouring of a single large slab ingot mold, or for use in pouring multiple ingots from a single ladle.

While substantially uniform rates of metal delivery can be produced by the use of a conventional ladle nozzle and a stopper rod with adroit throttling, such a method produces a very ragged stream of high surface to weight ratio conducive to excessively high oxidation rates and splattering of the metal in the mold. The nozzle must be preheated to a temperature approximating the temperature of the molten metal subsequently poured therethrough so as to avoid freezing of metal within the nozzle. The heat conductivity of the nozzle material must therefore be low so as to avoid cooling during operation. With such service the material must be able to withstand erosion, since either erosion or build up by metal freezing will change the dimensions of the bore and thus change the rate of pour through and the nature of the discharge "ice from the nozzle to the detriment of the casting process.

I have found that a novel mix of sintered magnesitechrome may be successively used in forming a pouring nozzle for passage of molten steel therethrough. The mix will analytically contain 3.6 to 7.5 FeO, 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O and to MgO, where the sum of the oxides of iron, aluminum, chrome and magnesium should be at least 70%. Additional oxides should not exceed 11.0% CaO, 8.6% Fe O and 8.7% SiO and with a ratio of RO/R O of 3 to 4. The material is mixed with 3 to 5% of a bonding agent such as Goulac, dextrin or the like, or dry sodium silicate. The mixture, with the bonding agent, is wetted with 6 to 7% (by weight) water, formed to the desired shape by conventional dry press techniques at conventional dry pressing pressures and dried. Thereafter, the nozzle is fired at 2700 to 2750 F. minimum, and cooled in a furnace to room temperature.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating ad vantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Of the drawings:

FIG. 1 is an elevation, in section, of a ladle and tun dish schematically arranged to deliver molten metal to a casting mold, and incorporating the nozzle of the present invention; and

FIG. 2 is an enlarged elevation, in section, of a portion of the apparatus shown in FIG. 1.

While the ceramic composition of the present invention is illustrated in the form of a pouring nozzle as used in the casting of ferrous metals and alloys, it will be understood the composition may be used for multiple nozzles in steel ingot casting, for purposes other than nozzles, and it may be used for metals other than ferrous alloys.

As shown in the drawings, a nozzle block 10' containing a nozzle 10 is positioned in the bottom 11 of a transfer ladle 12 where the rate of pour from the ladle is controlled by cooperation between the nozzle 10 bore dimensions and a movable stopper rod 13. The molten metal discharged from the ladle 12 passes through a tun dish 14 or similar flow channel for discharge through a nozzle 15 directly into the open upper end of a casting mold 16.

As shown in FIG. 1, the transfer ladle 12 includes a metal body lined with refractory material 17 of conventional construction. The ladle 12 may have a molten metal capacity of from 5 to 50 tons, or even greater. While it is of advantage to use a pouring nozzle 10 of the ceramic composition which forms the subject matter of this application, it is also possible to use a conventional fire clay ladle nozzle since erosion in the ladle nozzle 10 is not nearly as detrimental to the regulation of the pouring rate as erosion in the nozzle 15 which delivers molten metal directly to the casting mold 16. i

The ladle nozzle 10 is constructed in one piece with an upwardly tapered entrance end 18 when the nozzle block 10 is positioned in an opening 20 in the ladle bottom 11. As shown, the nozzle block is held in position by an angle iron framework 21 and is backed up by a ramming mix 22 to maintain the nozzle in its proper position relative to the refractory materials forming the remainder of the ladle bottom. The stopper rod 13 is of conventional construction where a steel rod 23 is vertically positioned in co-axial relationship with the center line of the nozzle. The stopper rod is normally protected by a layer of refractory material 24 and is provided with a stopper head 25fo'rmed of a graphite and clay mixture so that when the stopper 13 is moved to its lowermost position, the contact between the lower surface of the stopper head 25 and the upper tapered end portion 18 of the nozzle effects a tight closure to definitely stop movement of molten metal through the nozzle. In the normal course of operation, the stopper rod 13 is moved upwardly from the tapered upper end of the nozzle and positioned to regulate the flow of metal through the nozzle. As hereinafter described, the stopper rod positioning is used to regulate the rate of flow of molten metal to the tun dish 14 and thence to the continuous casting mold 16.

Thetun dish 14 is shown in greater detail in FIG. 2 and includes a metallic casing having steel plate sides 29 (only one shown) and ends 26 and 27 with a cast iron bottom 28. Ordinarily, the tun dish is of square or rectangular horizontal and vertical cross-section and is lined with a high aluminum refractory brick 30 capable of withstanding the heat and erosive effect of the molten metal passed therethrough. As shown, the tun dish 14 is provided with a depending baffle 31 which serves as a skimmer interposed across the flow path of the molten metal-moving from the inlet end 32 of the tun dish to the nozzle or discharge end 33 thereof.

The cast iron bottom of the tun dish is provided with an opening 34 of, for example, 2%" diameter. This opening is positioned closely adjacent the end wall 26 and intermediate the side walls 29 of the tun dish. A corresponding opening is provided through the refractory lining 30 of the tun dish for the insertion of the nozzle 15 of the present invention. The nozzle block 15' with its nozzle 15 is supported on insulating fire brick 36 resting on the bottom plate 28 adjacent the opening 34, and is positioned by a ramming mix 37 inserted between the nozzle and the adjacent refractory lining 30. The nozzle is formed With an inwardly tapering entrance end portion 35 which the bore of the nozzle is dimensioned to provide the proper flow rate therethrough consistent with the viscosity of the molten metal being handled. In the illustrated embodiment, the casting unit is capable of handling approximately 500 pounds per minute, with a bore diameter of the nozzle of and when a head of 8 to inches of molten low carbon steel is imposed thereon.

The nozzle is formed as a sintered chrome-magnesite composition where the chrome ore is of a special composition and size consist. The chrome ore used should be of a size wherein all of the ore will pass a 10 mesh screen (Tyler) and have the following fineness distribution:

Preferred cumulative The magnesite composition is also special, should all pass a 4 mesh screen (Tyler) and have the following fine ness distribution:

1 Preferred cumulative Tyler mesh: percent limits 21 to 43 to 50 +65 50 to 60 +100 53 to 62 +200 65 to 73 -200 100 In the raw mix the proportion of chrome ore to magnesite is in the approximate range of 30% (by weight) chrome ore and 70% (by weight) magnesite. For the best average properties of a nozzle, the mix should have the following chemical characteristics: FeO, 3.6 to 7.5%

Al O 4 to 7%; Cr O 9.3 to 15%; MgO 50 to 70%; and the sum of the above to be at least 70%. The following materials are also present in the mix in the amounts listed; SiO no more than 8.7%; CaO, no more than 11.0%; Fe O no more than 8.6%. All of the above to have a molecular ratio of RO/R O of 3 to 4.

I prefer to add to the above mixture approximately 3 to 5% of bonding agent to assure the necessary unfired strength for handling. This bonding agent may be obtained with organic bonds such as Goulac, dextrin or the like, or by the addition of similar amounts of dry sodium silicate. The mixture including the bonding material is wetted with 6 to 7% of water by Weight, and formed to the desired configuration by conventional dry press techniques. Thereafter, the nozzle is dried overnight at 200 C., fired at 2700 to 2750 F. minimum, and cooled in the furnace to substantially room tempenature.

Prior to use, the discharge end of the nozzle block 15 :is cut so as to produce a non-tapered portion of the nozzle 15 subjacent the tapered portion 35 of nozzle 15 of FIG. 2 equal to at least one bore diameter, the out being made so that the plane of the bottom surface is normal to the axis of the bore of the nozzle. Over a range of nozzle sizes this procedure results in cut nozzle blocks of various heights. The height of the insulation 36 is therefore varied to bring the top of the nozzle block 15 substantially flush with the uppermost surface of the bottom refractory liner 30 of the tun dish 14.

However, in nozzles as small as bore diameter we have found it advantageous and necessary to have the upper end of the nozzle block extend above the uppermost surface of the tun dish lining 30 to insure better heating of the nozzle block both during preheating, and by the metal being poured.

In forming the above mix, I have used chrome ore of the following compositions:

The magnesite compositions used in the mix have had ,the following analysis:

Composition Number (3), per' (4), per- Preferred cent cent (5), pen

cent

The chrome-magnesite consist formed by combining compositions 1 and 5 above, had the following analysis to form a preferred nozzle according to the invention:

In the above example of the composition the RO/R O factor is 3.28 and the nozzle proved to be entirely satisfactory for the purpose. Substantially equal success was attained by a mix of 30% (by weight) of composition 1 when combined with 70% (by weight) of composition 4. In such a composition the RO/R O factor is 3.37. Mixes formed by compositions 2 and 3, 2 and 4, and 2 and 5 were also successful with the RO/R O factors being 2.98, 4.06 and 3.96 respectively. However, a mix formed by combining compositions 1 and 3 in the described ratio had a RO/R O factor of 2.52 and proved to be too soft for satisfactory nozzle service in the continuous casting of steel.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form and mode of operation of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. A sintered refractory pouring nozzle for molten metal comprising a chrome-magnesite mix combined with a bonding agent and water, said mix being molded at a pressure in excess of 1000 psi to form a pouring nozzle and fired to a temperature of not less than 2700 to 2750 F., said chrome-magnesite mix analytically containing 3.6 to 7.5% FeO; 4.0 to 7.0% A1 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, Al O Cr O and MgO being at least 70%, and including no more than 11.0% CaO, 8.6% Fe O and 8.7% SiO 2. A sintered refractory pouring nozzle for molten metal comprising a chrome-magnesite mix combined with a bonding agent and water, said mix being molded at a pressure in excess of 1000 psi. to form a pouring nozzle, and fired to a temperature of not less than 2700 to 2750 F., said chrome-magnesite mix analytically containing 3.62% FeO; 4.55% A1 0 9.36% Cr O 64.12% MgO; 5.76% CaO; 8.5% Fe O and 4.13% SiO 3. A sintered refractory pouring nozzle for ferrous alloys comprising a chrome-magnesite mix formed of 30% by Weight of 10 mesh chrome ore and 70% by weight of -4 mesh magnesite combined with a bonding agent and water, said mix being molded at a pressure in excess of 1000 psi. to form a pouring nozzle, and fired to a temperature of not less than 2700 to 2750 F., said chrome-magnesite mix analytically containing 3.6 to 7.5 FeO; 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, A1 0 Cr 0 and MgO being at least 70%, and including no more than 11.0% CaO, 8.6% Fe O and 8.7% SiO 4. A refractory pouring nozzle for ferrous alloys comprising a chrome-magnesite mix formed of 30% 10 mesh chrome ore and 70% -4 mesh magnesite, said mix combined with 3 to 5% by weight of a bonding agent and 6 to 7% by weight of water, said mix being dry molded at a pressure in excess of 1000 psi. to form a pouring nozzle, and fired to a temperature of not less than 2700 to 2750 F., said chrome-magnesite mix analytically containing 3.6 to 7.5% FeO; 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, A1 0 Cr O and MgO being at least 70%, and including no more than 11.0% CaO; 8.6% Fe O and 8.7% SiO 5. A sintered refractory pouring nozzle for ferrous alloys comprising a chrome-magnesite mix formed by combining by weight 30% of chrome ore and 70% of magnesite, said chrome ore having a maximum size of 10 mesh and having a cumulative fineness percentage 6 of 7 to 15% on the 65 mesh screen, 17 to 24% on 100 mesh screen and 53 to 60% on 200 mesh screen, said magnesite having a maximum size of 4 mesh and having a cumulative fineness percentage of 50 to 60% on the 65 mesh screen, 53 to 62% on the 100 mesh screen and 65 to 73% on the 200 mesh screen, said chromemagnesite mix analytically containing 3.6 to 7.5 FeO; 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O 50 to MgO with the sum of FeO, A1 0 Cr O and MgO being at least 70%, and including no more than 11.0% CaO; 8.6% Fe O and 8.7% SiO 6. A molded sintered chrome-magnesite refractory shape analytically containing 3.6 to 7.5% FeO; 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, A1 0 Cr O and MgO being at least 70%, and including no more than 11.0% CaO; 8.6% Fe O and 8.7% SiO 7. A sintered refractory shape comprising a chromemagnesite mix combined with a bonding agent and water, said mix being molded at a pressure in excess of 1000 p.s.-i. to form a pouring nozzle, and fired to a temperature of not less than 2700 to 2750 F., said chrome-magnesite mix analytically containing 3.62% FeO; 4.55% A1 0 9.36% Cr O 64.12% MgO; 5.76% CaO; 8.5% Fe O and 4.13% SiO 8. A refractory shape comprising a chrome-magnesite mix formed of 30% by weight of 10 mesh chrome ore and 70% by weight of -4 mesh magnesite combined with a bonding agent and water, said mix being molded at a pressure in excess of 1000 p.s.i. to form said shape, and sintered at a temperature of approximately 2750 F., said chrome-magnesite mix analytically containing 3.6 to 7.5% FeO; 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, A1 0 Cr O and MgO being at least 70%, and including no more than 11.0% CaO, 8.6% Fe O and 8.7% SiO 9. A sintered refractory shape resistant to erosion by molten ferrous alloys comprising a ohrome-magnesite mix formed of 30% 10 mesh chrome ore and 70% 4 mesh magnesite, said mix combined with 3 to 5% by weight of a bonding agent and 6 to 7% by weight of Water, said mix being dry molded :at a pressure in excess of 1000 p.s.i. to form said shape, and fired to a temperature of not less than 2700 to 2750 F., said chrome-magnesite mix analytically containing 3.6 to 7.5 FeO; 4.0 to 7.0% Al O 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, A1 0 Cr O and MgO being at least 70%, and including no more than 11.0% CaO, 8.6% Fe O and 8.7% SiO 10. A sintered refractory shape resistant to erosion by molten ferrous alloys comprising a chrome-magnesite mix formed by combining by Weight 30% of chrome ore and 70% of magnesite, said chrome ore having a maximum size of 10 mesh and having a cumulative fineness percentage of 7 to 15% on the 65 mesh screen, 17' to 24% on mesh screen and 53 to 60% on 200 mesh screen, said magnesite having a maximum size of 4 mesh and having a cumulative fineness percentage of 50 to 60% on the 65 mesh screen, 53 to 62% on the 100 mesh screen and 65 to 73% on the 200 mesh screen, said chrome-magnesite mix analytically containing 3.6 to 7.5 FeO; 4.0 to 7.0% A1 0 9.3 to 15.0% Cr O 50 to 70% MgO with the sum of FeO, A1 0 Cr O and MgO being at lea-st 70%, and including no more than 11.0% CaO, 8.6% Fe O and 8.7% SiO References Cited in the file of this patent UNITED STATES PATENTS 2,068,641 Carrie et al Ian. 26, 1937 

1. A SINTERED REFRACTORY POURING NOZZLE FOR MOLTEN METAL COMPRISING A CHROME-MAGNESITE MIX COMBINED WITH A BONDING AGENT AND WATER, SAID MIX BEING MOLDED AT A PRESSURE IN EXCESS OF 1000 P.S.I. TO FORM A POURING NOZZLE AND FIRED TO A TEMPERATURE OF NOT LESS THAN 2700 TO 2750*F., SAID CHROME-MAGNESITE MIX ANALYTICALLY CONTAINING 3.6 TO 7.5% FEO; 4.0% AL2O3; 9.3 TO 15.0% CR2O3; 50 TO 70% MGO WITH THE SUM OF FEO, AL203, CR2O3 AND MGO BEING AT LEAST 70%, AND INCLUDING NO MORE THAN 11.0% CAO, 8.6% FE2O3 AND 8.7% SIO2. 